1. Field of the Invention
The present invention relates to a mutual-capacitance, projected-capacitive touch screen device that determines whether or not a touch is present based on an amount of change in a charge-discharge current at each intersection of electrodes arranged in a grid pattern.
2. Description of Related Art
There are various types of touch screen devices. A capacitive touch screen device does not require an electronic pen including an oscillator or the like, and a touch operation on the capacitive touch screen device can be performed directly with a finger tip of a user or with a stylus simply made of a conductive material.
A projected capacitive touch screen device includes first electrodes and second electrodes arranged in a grid pattern, and uses a principle that capacitance of a capacitor provided at each intersection (hereinafter, referred to as an electrode intersection) of the first electrodes and the second electrodes varies with a close access or a contact of a conductive object (e.g., human body).
A mutual-capacitance, projected-capacitive touch screen device detects whether a touch is present based on an amount of change in the charge-discharge current according to the change in capacitance at each electrode intersection, It is possible to perform multi-touch (or multipoint detection), which detects a plurality of touch positions simultaneously, in the mutual-capacitance, projected-capacitive touch screen device (see Related Art 1).
The touch screen device is widely used in fields of personal computers or handheld terminals. On the other hand, a technology is known in which the touch screen device is used as an interactive whiteboard, by combining the touch screen device with a large screen display device to be used in a presentation or a lecture for a large audience (see Related Art 2).    Related Art 1: Japanese Patent Application Publication No. 2002-342033    Related Art 2: Japanese Patent Application Publication No. 2009-86855